Combine T1's

I have two Cisco 1841 series routers with two T1 wics on each device. I currently have one T1 connected and working but want to add another T1 and share the load between the two. Is this possible with the 1841 series routers and does anyone know where I can find a config to support this type of connection. Thanks

Reply to
jester
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set" ip cef" in global mode then on each serial port add "ip load-sharing per-packet." Now do a traceroute from your ether port to your ISPs gateway and watch the serial ports load share. Some ISPs, like Sprint will not assign a global ip to the serial ports-they indicate it cuts down on DOS attacks.

Nonetheless, if you are using a protocol that assumes in sequence packets this may cause some problems. Cisco's default is to use one serial port per source-destination packet flow--load shares per flow. Turn CDP off on each serial port unless absolutely needed.

I am assuming your vers of IOS supports this and I have never used the 1841.

Hope this helps as I was in a hurry when I composed this reply.

Digital Doug

Reply to
Houston SBC

Even if it's not assumed, out-of-sequence packets cause more work for everyone involved. MultilinkPPP is a better option here:

interface Serial0/0 no ip address encapsulation ppp ppp multilink ppp multilink group 1 ! interface Serial1/0 no ip address encapsulation ppp ppp multilink ppp multilink group 1 ! interface Multilink1 ip address 10.1.1.1 255.255.255.252 ppp multilink ppp multilink group 1 ppp multilink fragment disable

Disabling fragmentation lessens the workload on the routers, as it will round-robin whole packets, and sequence them properly when routing them to the LAN

This assumes routers with p2p T1's - no L3 service provider in the middle

Reply to
Tom Lawrence

Thanks to both of you for your help. I have VOIP going over this line and the issue that I am worried about is packets arriving out of sequence. I am glad to see the multilink setup and I appreciate your time in this post. I will give it a go and try to make it work. Thanks again.

Tom Lawrence wrote:

Reply to
jester

You'll also want to have QoS configured for your VoIP traffic, as well. Something along the lines of:

class-map match-any voice match dscp ef policy-map voip class voice priority 216 class class-default fair-queue ! interface Multilink1 service-policy output voice

Adjust the 'priority xxx' number to a kilobit value to support your maximum number of simultaneous VoIP calls. This also assumes your VoIP end stations mark their traffic with DSCP value 'ef' (decimal 46). If the end stations don't support DSCP, but do IP precedence instead, change the match entry in the class map to 'match ip precedence 5' (the conventional precedence value for real-time traffic)

Reply to
Tom Lawrence

Great! I will give this a try. Thanks

Tom Lawrence wrote:

Reply to
jester

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